During the last year our research core has worked with ten NIH research units to generate novel embryonic stem cell lines (20 projects, most of them using CRISPR/Cas9 transfections) and new mouse models (34 projects, including 6 CRISPR/Cas9 Zygote injections). This research included establishment of models to study disease associated with RNAse H dysfunction, signal pathway interactions in the immune system, T cell development, hematopoiesis, stem cell biology, epigenetic inheritance in the early embryo, mechanisms regulating genomic stability, RNA metabolism, genetic disorders in bone and extracellular matrix, gene regulation and enhancer function, nervous system development, iron methabolism and malaria risk, and endocrine and cancer genetics. We also performed cryopreservation of 10 mouse lines, derived 8 novel embryonic stem cell lines from genetically altered mice, and re-derived 10 mouse strains. We also performed thymus implants. In the past year we developed further expertise to perform zygote injections (nuclear and cytoplasmic) and will offer these services to the NICHD research community.